When in an argument which you are losing, simply demand to know what secrets your opponent is hiding from you. When your opponent, surprised most likely, retorts that they don't know what the hell you're on about, you look at them funny for a moment, then storm furiously out of the place you're holding the argument in. This not only makes you "win" the argument, but you also make your opponent slightly nervous as they probably ARE hiding something from you.

Clark: but lana, I saw you kissing with Lex! why did you do that?!
Lana: Clark, what's your secret? why are you hiding it from me? don't you trust me?
Clark: what does that have to do with anything?
*lana lang storms out of clarks loft, leaving him confused and annoyed at her.. but she still won the damn argument*